Alternating plasma panels are known in the prior art, and are published in French patent application No. 78.04893, delivered under No. 2 417 848, in the name of Thomson-CSF, and in an article published in Revue Technique Thomson CSF, June 1978, vol. 10, No. 2, pp. 249-275.
These panels comprise a large number of cells arranged in matrix formation. Each cell consists of the gaseous space situated at the intersection between two electrodes belonging to two orthogonal electrode networks, and is subject to control signals consisting of the difference in voltages applied to the two electrodes between which it is situated.
Control signals comprise setting signals turning cells on, clearing signals turning them off, and maintenance signals, which keep them in their initial state, whether off or on.
Unlike maintenance signals, which are applied to all electrodes in the panel in order to display information, setting and clearing signals are selective signals, which turn only selected cells on and off.
Consequently, a given cell C.sub.xy is set only if both its electrodes x and y receive appropriate voltages V.sub.x and V.sub.y, which produce the setting signal at only the terminals of that cell.
The same conditions apply to the clearing of this cell.
In the prior art, the voltages V.sub.x and V.sub.y to set cell C.sub.xy are different from the voltages V'.sub.x and V'.sub.y needed to reset it.
Consequently, it is not possible to obtain simultaneous assorted setting and clearing of cells sharing an electrode, namely cells located on the same line or column of the panel.
There is therefore a problem with alternating plasma panels when displaying successive images, such as television pictures.
It is impossible to set the images quickly, i.e. with a setting time for each line of approximately 20 .mu.s, and to make the images succeed one another quickly, indeed more or less uninterruptedly.
It should be remembered that alternating plasma panels store every image set on them. Since selective cell setting and clearing cannot be obtained simultaneously for a given line, the panel has to be cleared before a new image is entered.
It is possible:
either to clear the whole panel at once, then set a new image, line by line, the disadvantage here being that the different lines of the panel do not have the same display time, so that brightness varies from one line to another; this image defect increases with the speed of changes of images;
or to clear one or several lines of the panel, then set them line by line, the disadvantage here being that setting time for each image is greatly increased, in fact even doubled, where only one line is cleared before setting it again: approximately 2.times.20 .mu.s is needed to set one line.
This invention offers a way of overcoming the problem of image display by means of alternating plasma panels, by removing the drawbacks of brightness variation and increase of setting time, without altering the memory capacity of such panels.